The Brotherhood is banned but mainly tolerated by the authorities

A report from the Egyptian Organisation for Human Rights says security forces hit peaceful protesters with sticks and used rubber bullets and tear gas.

One man died in the Nile delta town of Mansoura earlier this month during a series of nationwide protests.

Officials say he was crushed, but the Brotherhood says police hit his head.

The EOHR report also says it has the names of nearly 500 members of the Brotherhood who were detained by security forces.

"Security approaches to dealing with the Muslim Brotherhood's peaceful demonstrations and the campaign of detentions against the group are a danger signal for the right to peaceful assembly and freedom of opinion and expression ... guaranteed in the constitution," the group says.

The demonstrations by the Muslim Brotherhood on 5 May were the largest of a series such protests calling for political reform that Egypt has witnessed this year.

Correspondents say the police response was more severe than that used against the mainly secular Kifaya Movement, which has also staged protests against a fifth term in office for President Hosni Mubarak.